I just need an hour!

I am co-writing a book with another woman and we are about 2/3 done.  We plan to finish this draft in four weeks but some days (like today) I'm wondering how that is going to be possible.  I really just need one quiet hour to add 800-1000 words (first draft quality).  It should be easy, right?  But today I am trying to get back on track.  I've been neglecting laundry and dinner and exercising for about 4 weeks now doing publicity for The Hate and Secrets.  Today I did laundry, took some of the kids to a camp, made dinner, cleaned the kitchen, made lunch, and went to the gym.  It is now almost 2 pm and I am outside because my other two kids begged me to let them ride their bikes.  In less than two hours I have to go get my first two kids from camp.  Then all four will be home and there is no way I'll get anything done after that.  I should mention my kids are 7, 6, 4, and 3.  I can pretty much only work when they are not home or sleeping.
Now I'm not blaming this on the kids.  When I think back to my life before kids, I'm trying to remember how much free time I had back then.  It didn't feel like much but I'm sure there was plenty.
So, how does everyone do it?  How do you manage to find time to write?  I'd love to hear your tips.